Type Synthesis of a Family of Novel Four, Five, and Six Degrees-of-Freedom Sea Lion Ball Mechanisms With Three Limbs

2016 ◽  
Vol 8 (2) ◽  
Author(s):  
Rongfu Lin ◽  
Weizhong Guo ◽  
Feng Gao
Keyword(s):  
Mathematical Models ◽  
Degrees Of Freedom ◽  
Type Synthesis ◽  
Sea Lion ◽  
End Effector ◽  
Motion Patterns ◽  
Six Degrees Of Freedom ◽  
Rotational Motions ◽  
The Given ◽  
Actuated Joints

A family of novel mechanisms with three limbs called sea lion ball mechanisms (SLBMs) is investigated that looks like a sea lion playing with a ball. The SLBM-type mechanism is composed of an upper part and a lower part connected together by three limbs in parallel, and the translational and rotational motions are fully/partially decoupled. The end-effector position is determined by inputs of the lower part, while the posture is mainly determined by inputs of the upper part. First, two compositional principles are abstracted and the corresponding mathematical models are built for the SLBM-type mechanisms that the commutative feature of the SLBMs is found. Then, two type synthesis procedures containing five steps are proposed correspondingly. Following the procedure, a family of novel four, five, and six degrees-of-freedom (DOF) SLBM-type mechanisms is synthesized systematically. The motion patterns of the limbs are enumerated according to the given desired ones of the mechanisms and the limbs are synthesized correspondingly. Finally, several novel SLBM-type mechanisms are achieved by assembling the obtained limbs and selecting the actuated joints.

Type Synthesis of a Family of 4-, 5- and 6-DOF Sea Lion Ball Mechanisms With Three Limbs

2015 ◽  
Author(s):  
Rongfu Lin ◽  
Weizhong Guo ◽  
Feng Gao
Keyword(s):  
Synthesis Method ◽  
Lower Limbs ◽  
The Novel ◽  
Type Synthesis ◽  
Sea Lion ◽  
End Effector ◽  
Motion Patterns ◽  
In Series ◽  
Rotational Motions ◽  
Sets Theory

In this paper, a family of novel mechanisms with three limbs is proposed. The novel family of mechanisms looks like a sea lion playing a ball therefore we called it the sea lion ball mechanism (SLBM). Its characteristics are described in detail below. The SLBM is composed of an upper part and a lower part connected together by three limbs in series. One of the most important advantages of SLBMs is that the translational and rotational motions are partially decoupled: the end-effector position is only determined by the inputs of the lower part, while the rotational angles are mainly determined by the inputs of the upper part. Then, the procedures for the type synthesis of SLBMs with three limbs are proposed based on the GF sets theory and the concept of virtual chain. Furthermore, according to the proposed procedure, 4-, 5- and 6-DOF SLBMs are investigated in terms of type synthesis based on a concept of upper-lower combination. The synthesis method of the upper limbs and lower limbs are presented. The PR and Pa joints are introduced to realize the functions of R and P joints to achieve more mechanisms. The six types kinematic limbs with 3T3R, 3T2R, 2T3R, 3T1R, 2T2R and 1T3R motion patterns of SLBMs are designed. Lastly, several novel 4-, 5- and 6-DOF SLBMs are proposed and sketched. The concept of the upper-lower combination may provide a new idea for type synthesis of decoupled parallel mechanism.

Experimental Validation of the Kinematics of a 3PRS Compliant Mechanism for Micromilling

2015 ◽  
Author(s):  
Antonio Ruiz ◽  
Francisco Campa Gomez ◽  
Constantino Roldan-Paraponiaris ◽  
Oscar Altuzarra
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Experimental Validation ◽  
Compliant Mechanism ◽  
Motion Controller ◽  
End Effector ◽  
Compliant Joints ◽  
Hybrid Manipulator ◽  
Compliant Parallel Mechanism ◽  
Actuated Joints

The present work deals with the development of a hybrid manipulator of 5 degrees of freedom for milling moulds for microlenses. The manipulator is based on a XY stage under a 3PRS compliant parallel mechanism. The mechanism takes advantage of the compliant joints to achieve higher repetitiveness, smoother motion and a higher bandwidth, due to the high precision demanded from the process, under 0.1 micrometers. This work is focused on the kinematics of the compliant stage of the hybrid manipulator. First, an analysis of the workspace required for the milling of a single mould has been performed, calculating the displacements required in X, Y, Z axis as well as two relative rotations between the tool and the workpiece from a programmed toolpath. Then, the 3PRS compliant parallel mechanism has been designed using FEM with the objective of being stiff enough to support the cutting forces from the micromilling, but flexible enough in the revolution and spherical compliant joints to provide the displacements needed. Finally, a prototype of the 3PRS compliant mechanism has been built, implementing a motion controller to perform translations in Z direction and two rotations. The resulting displacements in the end effector and the actuated joints have been measured and compared with the FEM calculations and with the rigid body kinematics of the 3PRS.

scholarly journals Redundancy Resolution Using Tractrix: Simulations and Experiments

2009 ◽  
Author(s):  
V. C. Ravi ◽  
Subrata Rakshit ◽  
Ashitava Ghosal
Keyword(s):  
Degrees Of Freedom ◽  
Redundancy Resolution ◽  
Redundant Manipulator ◽  
End Effector ◽  
Redundant Robots ◽  
Natural Motion ◽  
Fixed Base ◽  
Effective Use ◽  
Actuated Joints ◽  
Present Simulation

Hyper-redundant robots are characterized by the presence of a large number of actuated joints, many more than the number required to perform a given task. These robots have been proposed and used for many application involving avoiding obstacles or, in general, to provide enhanced dexterity in performing tasks. Making effective use of the extra degrees of freedom or resolution of redundancy have been an extensive topic of research and several methods have been proposed in literature. In this paper, we compare three known methods and show that an algorithm based on a classical curve called the tractrix leads to a more ‘natural’ motion of the hyper-redundant robot with the displacements diminishing from the end-effector to the fixed base. In addition, since the actuators at the base ‘see’ the inertia of all links, smaller motion of the actuators nearer to the base results in a smoother motion of the end-effector as compared to other two approaches. We present simulation and experimental results performed on a prototype eight link planar hyper-redundant manipulator.

A Dual-Stage Planar Cable Robot: Dynamic Modeling and Design of A Robust Controller with Positive Inputs

2004 ◽  
Vol 127 (4) ◽  
pp. 612-620 ◽  
Author(s):  
So-Ryeok Oh ◽  
Kalyan Mankala ◽  
Sunil K. Agrawal ◽  
James S. Albus
Keyword(s):  
Degrees Of Freedom ◽  
Robust Controller ◽  
Two Stage ◽  
End Effector ◽  
Six Degrees Of Freedom ◽  
Cable Robot ◽  
Unknown Disturbances ◽  
Dual Stage ◽  
Loading And Unloading ◽  
Skin To Skin

Cable robots have potential usage for loading and unloading of cargo in shipping industries. A novel six-degrees-of-freedom two-stage cable robot has been proposed by NIST for skin-to-skin transfer of cargo. In this paper, we look at a planar version of this two-stage cable robot. The disturbance motion from the sea is considered while modeling the dynamics of robot. The problem of robust control of the end-effector in the presence of unknown disturbances, along with maintaining positive tensions in the cables, is tackled using redundancy of cables in the system. Simulation results show the effectiveness of the control strategy.

A Fourier Descriptor Approach to Integrated Type and Dimensional Synthesis of Coupled Serial Mechanism for Motion Generation

2019 ◽  
Author(s):  
Hao Lv ◽  
Yuanfei Han ◽  
Xiangyun Li ◽  
Liuxian Zhu
Keyword(s):  
Fourier Descriptor ◽  
Dimensional Synthesis ◽  
Type Synthesis ◽  
Motion Generation ◽  
End Effector ◽  
Novel Approach ◽  
Descriptor Approach ◽  
Harmonic Components ◽  
The Given ◽  
Serial Mechanism

Abstract Coupled serial mechanism is a class of mechanisms that couple the relative rotation of successive links utilizing gears or cable-pulley systems. They can be used to generate complex end-effector trajectories or motions with a single actuator. With the employment of Fourier descriptors, a novel approach to integrate type synthesis and dimensional synthesis of such mechanisms is proposed in this paper. Through the Fourier analysis of two arbitrary trajectories from the given motion, the simplest trajectory that contains the least number of harmonic components is identified. Then, characteristic information of those harmonics such as their numbers, amplitudes and initial phases are used to determine the topology and dimensions of the corresponding coupled serial mechanism, thus effectively solving the motion synthesis problem of this type of mechanisms. Finally, three examples are given to demonstrate the validity of the proposed method.

Development of a Haptic Device with Wire-Driven Parallel Structure

2017 ◽  
Vol 11 (3) ◽  
pp. 385-395
Author(s):  
Carlo Ferraresi ◽  
◽  
Carlo De Benedictis ◽  
Francesco Pescarmona
Keyword(s):  
Degrees Of Freedom ◽  
Force Feedback ◽  
Parallel Structure ◽  
Control Logic ◽  
End Effector ◽  
Six Degrees Of Freedom ◽  
Force Closure ◽  
Force Reflection ◽  
Definition Of ◽  
Selection Of

This study focuses on the specific problems that may arise in the development of a parallel, cable-driven device designed for teleoperations systems utilizing force-reflection feedback. A redundant six degrees-of-freedom structure, actuated by nine wires, is described as a convenient layout for a haptic master for telemanipulation. A methodology for the kinematic and static analysis and the evaluation of the device workspace is described. The condition of force closure is used to find all available poses of the end-effector, thereby defining the workspace, whose characteristics are assessed by opportunely conceived indexes. Typical characteristics of cable and implementations thereof in the device are considered. Regarding the realization of the device, relevant attention is given to the definition of the control logic, which can be complex for parallel devices. The selection of the actuators, crucial in realizing force feedback, is discussed. In particular, pneumatic actuation is considered, verified as the most appropriate method for implementation and force control of the cylinders.

Design, testing and evaluation of an end-effector for self-relocation

Robotica ◽  
2015 ◽  
Vol 34 (12) ◽  
pp. 2689-2728 ◽  
Author(s):  
Feng Han ◽  
Kui Sun ◽  
Yu Liu ◽  
Hong Liu
Keyword(s):  
Degrees Of Freedom ◽  
Physical Simulation ◽  
Industrial Robot ◽  
Space Environment ◽  
Air Bearing ◽  
End Effector ◽  
Six Degrees Of Freedom ◽  
Soft Capture ◽  
End Effectors ◽  
Prototype Design

SUMMARYTwo identical end-effectors are indispensable for self-relocation of a space manipulator, which is an effective way of extending its servicing capability. The prototype design is intimately linked to the requirements. The significant features and functionality of the end-effector and its grapple fixture are described, including the key analysis efforts. The characteristics of the end-effector and their suitability for self-relocation and payload handling were confirmed by testing, which used two prototype end-effectors, a semi-physical simulation testbed system with two, six degrees of freedom (DOF) industrial robot arms, and an air-bearing testbed system with a seven DOF manipulator. The results demonstrate that the end-effector satisfies the requirements and it can work well in a simulated space environment. With the compliance motion of the manipulator, the end-effector can perform soft capture and the manipulator can securely self-relocate and handle the payload.

Solving reachable workspace of some parallel manipulators by computer-aided design variation geometry

2008 ◽  
Vol 222 (9) ◽  
pp. 1773-1781 ◽  
Author(s):  
Y Lu ◽  
Y Shi ◽  
B Hu
Keyword(s):  
Computer Aided Design ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Six Degrees Of Freedom ◽  
Reachable Workspace ◽  
Spline Curves ◽  
Computer Aided ◽  
Design Variation ◽  
Aided Design ◽  
The Given

To shape the workspace of some novel parallel manipulators (PMs) is significant. A novel computer-aided design (CAD) variation geometry approach is proposed to shape and solve the reachable workspace of some PMs with three to six degrees of freedom (DOFs). Some basic techniques are described for designing the simulation mechanism and solving the reachable workspace. The simulation mechanisms of some PMs with three to six DOFs are created. When varying the driving dimensions of the active legs in the given extent, the simulation mechanisms vary correspondingly, and the position components of the moving platform are solved automatically. By transferring the position solutions into spatial spline curves in the simulation mechanism, all the boundary surfaces of the workspace can be created and visualized dynamically. Comparing with analytic approaches for solving workspace, the CAD variation geometry approach is simple, straightforward, accurate, and repeatable.

Kinematic model to control the end-effector of a continuum robot for multi-axis processing

Robotica ◽  
2015 ◽  
Vol 35 (1) ◽  
pp. 224-240 ◽  
Author(s):  
Salvador Cobos-Guzman ◽  
David Palmer ◽  
Dragos Axinte
Keyword(s):  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Euler Angle ◽  
Inverse Kinematic ◽  
End Effector ◽  
Six Degrees Of Freedom ◽  
Hazardous Environments ◽  
Continuum Robot ◽  
Novel Method ◽  
Six Dof

SUMMARYThis paper presents a novel kinematic approach for controlling the end-effector of a continuum robot for in-situ repair/inspection in restricted and hazardous environments. Forward and inverse kinematic (IK) models have been developed to control the last segment of the continuum robot for performing multi-axis processing tasks using the last six Degrees of Freedom (DoF). The forward kinematics (FK) is proposed using a combination of Euler angle representation and homogeneous matrices. Due to the redundancy of the system, different constraints are proposed to solve the IK for different cases; therefore, the IK model is solved for bending and direction angles between (−π/2 to +π/2) radians. In addition, a novel method to calculate the Jacobian matrix is proposed for this type of hyper-redundant kinematics. The error between the results calculated using the proposed Jacobian algorithm and using the partial derivative equations of the FK map (with respect to linear and angular velocity) is evaluated. The error between the two models is found to be insignificant, thus, the Jacobian is validated as a method of calculating the IK for six DoF.

Geometric synthesis of spatial parallel manipulators with fewer than six degrees of freedom

2002 ◽  
Vol 216 (12) ◽  
pp. 1175-1185 ◽  
Author(s):  
T S Zhao ◽  
J S Dai ◽  
Z Huang
Keyword(s):  
Mechanism Design ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Algebraic Approach ◽  
Structural Complexity ◽  
Parallel Manipulators ◽  
Parallel Mechanisms ◽  
Kinematic Pair ◽  
Type Synthesis ◽  
Six Degrees Of Freedom

Manipulators with fewer than six degrees of freedom meet specific tasks and have the advantage of reducing structural complexity, design redundancy and cost. In order to construct parallel manipulators for given tasks, this paper develops an algebraic approach to type synthesis of spatial parallel mechanisms with fewer than six degrees of freedom based on the screw theory. With the proposed steps (i.e. describing restraining screws, identifying basic kinematic pair (KP) screws reciprocal to the restraining screws, linearly transforming the basic KP screws to obtain equivalent serial limbs and allocating the serial limbs) new parallel mechanisms can be constructed. The approach converts a mechanism design into a screw algebra operation, in which screws describe kinematic pairs and constraints between links. As examples, synthesis procedures of parallel mechanisms with four degrees of freedom are given, from which five novel parallel mechanisms result.

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